1. Field of the Invention
The present invention generally relates to a starter with a speed reduction mechanism that decelerates the starter motor rotation and conveys the speed reduced rotation to an engine of a vehicle.
2. Related Art
Motors used in conventional starters extend the upper and lower armature cores held in the armature core slot in an axial direction, and form the circumference of the upper armature coil so that it is smaller in diameter than the armature core outer circumference to contact the brush against the cylinder's outer circumference as shown in Japanese Patent Laid-Open No. 1-218341. A current flows to the upper and lower armature coils from the brush using this structure.
However, when the conventional motor is applied to a starter with a speed reduction mechanism, a large centrifugal force is applied to the commutator surface of the armature coil because the motor is driven at a high speed. Due to the centrifugal force, a large mechanical load is applied to the molded resin cylinder that holds the armature coil and acts as the brush contact surface. Furthermore, the resistance heat generated between the brush and the commutator of the starter and the reduction mechanism is large because the motor is driven at a high speed, and a large thermal load is applied to the molded resin cylinder that holds the armature coil which acts as the brush contact surface.
In other words, if the conventional motor is applied to a starter having a reduction mechanism or to a starter with a reduction mechanism with higher reduction ratio, the mechanical load and thermal load increase. Therefore, the conventional motor cannot be applied to a starter with a reduction mechanism.